Unloader in refrigeration system



July 12, 1955 R. L. DILLS UNLOADER IN REFRIGERATION SYSTEM Invento Raymond L. Bills, 9

Filed Jan. 10, 1952 His Attorneg.

United States Patent Ofiice Z,?l2,735 Patented July 12, 1955 2,712,735 UNLOADER IN REFRIGERATION SYSTEM Raymond L. Dills, Erie, Pa., assignor to General Electric Company, a corporation of New York My invention relates to refrigeration apparatus and pertains more particularly to means for controlling the unloading and loading of compressors in refrigerating systems.

From the standpoint of economy in construction, operation and space, it is desirable to employ a small efiicient motor for driving the compressor in a refrigerating system. Such a motor has a low starting torque and therefore it is essential to its elficient operation that means he provided for permitting the motor when starting to develop maximum torque before any substantial load is placed on the compressor.

Accordingly, it is the primary object of my invention to provide in a refrigerating system an improved arrangement for unloading the compressor in the system to permit the motor driving the compressor to develop maximum torque when starting before any substantial load is placed on the compressor.

Another object of my invention is to provide in a refrigerating system an improved arrangement wherein the compressor in the system is unloaded during idle periods thereof and loading of the compressor is dependent upon operation of the motor driving the compressor.

Still another object of my invention is to provide a compressor unloading and loading means which is simple in construction, inexpensive in manufacture and contains a minimum of moving parts subject to wear.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In carrying out the objects of my invention, I provide a refrigerating system including an evaporator and a refrigerating unit. The refrigerating unit includes a compressor and a motor for driving the compressor. A suction line connects the low pressure side or intake port of the compressor with the evaporator. A check valve in the suction line is arranged to be open during normal operation of the compressor for permitting loading of the compressor from the evaporator. I provide a chamber in the suction line between the check valve and the compressor. The compressor includes means whereby equalization of pressures between the high and low pressure sides thereof is effected when the unit becomes idle. This equalization of pressures closes the check valve and fills the chamber and the suction line between the check valve and the low pressure side of the compressor with a refrigerant charge substantially equal in pressure to the refrigerant pressure at the high pressure side of the compressor. Thus, the compressor is unloaded. The volume of the chamber and the suction line between the check valve and the low pressure side of the compressor is such as to permit the compressor to come up to speed and the motor to develop maximum torque when starting before the pressure of the charge in the chamber and suction line is reduced by the compressor sufficiently to effect opening of the check valve and loading of the compressor.

For a better understanding of my invention, reference may be had to the accompanying drawing in which Fig. 1 is a schematic illustration of a refrigerating system incorporating my invention; Fig. 2 is an enlarged fragof the refrigerating unit; Fig. 3 1s a fragmentary section taken along the line 3-3 of Fig. 2 and looking in the direction of the arrows; Fig. 4 is a longitudinal sectional view of the check valve; and Fig. 5 is a section taken along the line 5-5 in Fig. 4 and looking in the direction of the arrows.

In Fig. l, I have shown a refrigerating system generally designated 1 and including a refrigerating unit 2, a condenser 3 connected to the refrigerating unit, and an evaporator 4. A suction line 5 connects the evaporator 4 with the refrigerating unit. A capillary tube 6 placed in heat exchange relationship with the suction line 5 connects the condenser 3 with the evaporator 4.

The refrigerating unit 2 includes a hermetically sealed case 7. The case 7 houses in the lower part thereof a rotary compressor generally designated 8 and in the upper part a motor (not fully shown) for driving the compressor. The motor is small and has a low starting torque. It operates most efficiently when it has developed its maximum torque.

The rotary compressor 8 includes an upper frame 9 and a lower frame 10 spaced apart by an annulus 11. A cover plate 12 secured to the under side of the lower frame It) cooperates with an inverted annular channel 13 formed in the lower frame 10 to provide an exhaust chamber 14. As better seen in Fig. 3, the annulus 11 is located concentrically with respect to a vertical crankshaft 15. The crankshaft 15 is suitably connected to the motor in the unit and portions of the crankshaft lower frames and in substantially the same plane as the annulus 11 is an eccentric 16. A rotor 17 is carried rotatably on the eccentric 16 and when the shaft 15 rotates the rotor operates eccentrically in the annulus 11.

haust port 20, also formed in the annulus 11. The intake port 19 is suitably connected to the end of the suction line 5'. The exhaust port 26 exits into the exhaust chamber 14. Positioned slidably in the radial slot 18 is a blade 21. Provided for maintaining a satisfactory oil seal about the blade 21 is a cup or reservoir 22. The cup 22 is fitted in the slot 18 at the outer end thereof. The bottom edge of the cup is suitably secured as by Welding to the lower frame 10 and the sides of the cup are similarly secured to the annulus 11. A compression spring 23 having one end seated in a bore 24 in the blade 21 and the other end seated in a similar bore 25 in the outer wall of the cup 22 causes the blade 21 to follow the surface of the rotor as it rotates eccentrically in the annulus 11 for thereby dividing the compressor into high and low pressure sides.

During normal operation of the refrigerating unit 2, a mixture of vaporous refrigerant and oil is drawn from the evaporator 4 through the suction line 5 and into the intake port 19 of the compressor. Movement of the rotor 17 causes the mixture of refrigerant and oil to be compressed and expelled from the exhaust port 20 into the exhaust chamber 14. A tube 26 conducts the compressed mixture of gas and oil to an annular passage 27 formed about the upper frame 9. In the passage 27 the gas and oil separate. The compressed gas is conducted by suitable means (not shown) from the case to the condenser 3 in the system. A passage 28 in the upper frame 9 permits of radial tabs 42.

c5 drainage of the separated oil, designated 29 in Fig. 2, from the annular chamber 27 into a trough 36 formed in the upper frame. Another passage 31 formed in the upper frame 9 and near the bottom or the trough 3t? directs the oil 29 into the cup 22 for maintaining a satisfactory oil seal about the blade 21. As in icated in Fig. 2, the cup 22 is maintained filled to overflowing. The overflow oil drains to the bottom of the case 7.

A spiral groove 32 is formed in the crankshaft 155 between the bottom end thereof and the eccentric 3.6. The cover plate 12. includes at least one oil hole 33. The spiral groove 32 draws oil through the hole 33 from the supply thereof in the bottom of the case and conveys it up and around the shaft to the underside of the eccentric 1.6. A vertical groove 34 in the eccentric lfi'permits' the .oil to flow from the underside of the eccentric to the upper side thereof On the upper side of the eccentric the oil is delivered up and around the upper portion of the crankshaft 15 and to the top of the frame by another spiral groove 35. From the top of the frame 9 the oil is dumped into the trough 30. In this manner oil is both deposited on the crankshaft and rotor for lubricating purposes and is delivered to the trough for assisting in supplying the cup 22 to seal the blade 21.

The pressure in of the compressor, is greater than that in the suction line 5, or at the low pressure side of the compressor. As a result, when the unit becomes idle, the blade seal is blown from the case across the surface of the oil in the cup 22 and into the suction line 5 through the intake port 19. In this manner, the pressures between the high and low pressure sides of the compressor cylinder are equalized substantially immediately when the unit becomes idle.

Included in the suction line 5 is a check valve 36. As

.seen in Figs. 4 and 5, the check valve 36 comprises a housing 37, a valve seat 38, a stop 39 and a disk 4% disposed between the seat and stop. The stop 39 is formed to include a plurality of legs 41 extending toward the disk 40. The disk 4t) is formed to include a plurality When the disk 40 is held against the valve seat 38, the flow of refrigerant from the evaporator 4- to the intake port 19 of the compressor 8 is stopped. When the disk 40 is not held against the valve seat 33, that is, when the disk rests on the legs 41 extending from the stop 39, refrigerant is permitted to fiow through the spaces between the radial tabs 42 and between the legs 41 on the stop 39 to the intake port of the compressor.

Also included in the suction line and located between the check valve 36 and the intake port 19 of the compress'or is a chamber 43. When the refrigerating unit stops and the pressures are equalized in the manner above described, the chamber 43 and the portions of the suction line 5 between the check valve 36 and the intake port 19 become filled with a refrigerant charge substantially equal in pressure to condenser pressure or the pressure on the high pressure side of the compressor. pressure of the refrigerant charge, therefore, is greater than that of the refrigerant in the evaporator 4 and as a result the disk at is held against the valve seat 38 in the check valve 36. This closes the check valve and retains the high pressure charge on the low pressure side of the compressor whereby the compressor is unloaded.

As pointed out above, the motor by which the compressor 8 is driven has a small starting torque and operates most efficiently when permitted to develop maximum torque before any substantial load is placed on the compressor. The compressor when starting requires a predetermined number of revolutions to come up to operating speed. The displacement of the compressor during each revolution multiplied by the predetermined number of starting revolutions required thereby amounts to a predetermined volume or the capacity of the compressor during starting periods. The combined volume of the chamber 43 and the suction line between the check valve 36 and the intake port 19 is at least equal to the capacity of the case'7, or at the high pressure side The the compressor during the starting period. Optimum combined volume for the chamber and suction line between the check valve and intake port has been found to be approximately one and one-half to two tirnes the capacity of the compressor during the starting period. This optimum volume may also be described as being approximately fifteen times the volume displaced by the compressor during one revolution.

When the refrigerating unit starts, the first revolution of the compressor purges the system of oil and on the succeeding revolution it draws in some of the high pres.- sure gas charge at the intake port and does some work of compression on it. This high pressure charge, however, is substantially equal to the condenser pressure and, therefore, does not load the compressor. It requires the predetermined number of starting revolutions of the compressor to purge the high pressure charge or to reduce the pressure thereof to evaporator pressure. When the pressure of the charge is so reduced, the check valve 36 opens and the compressor is again loaded from the evaporator for resuming its normal operation. By this time, the compressor has come up to operating speed and the motor is developing maximum torque.

As seen in Fig. l, the check valve 36 is located in the system 1 near the cabinet seal 44. This location of the check valve allows some of the gas to condense. Also, it will be clear after studying Fig. 1 that the chamber 43 is employed merely to conserve space. Other means such as a lengthy suction line or a coiled suction line could be employed for providing the volume required in the present arrangement between the check valve and the intake port.

While I have shownand described a specific embodiment of my invention, 1 do not desire my invention to be limited to the particular form shown and described, and I intend by the appended claims within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a refrigerating system including an evaporator, the combination of a refrigerating unit including a compressor having high and low pressure sides and a motor for driving said compressor, and means for unloading and loading said compressor comprising a suction line connecting said low pressure side of said compressor with said evaporator, 21 check valve in said suction line, said check valve being open during normal operation of said compressor for permitting loading of said compressor from said evaporator, means effecting equalization of pressures between said high pressure side of said compressor and said low pressure side thereof when said compressor becomes idle, said equalization of pressures increasing the pressure on the compressor side of said check valve and thereby closing said check valve, said equalization of pressures filling said suction line between said check valve and said low pressure side of said compressor with a refrigerant charge substantially equal in pressure to the refrigerant pressure at said high pressure side of said compressor whereby said compressor is unloaded, and the volume of said suction line between said check valve and said low pressure side'of said compressor being sufficient to permit said motor to develop 'maximum torque when starting before the pressure 'of said charge between said check valve and said compressor is reduced by said compressor sufficiently to effect opening of said check valve and normal loading of said compressor. 7

2. In a refrigerating system including ,an evaporator, the combination of a refrigerating unit including a compressor having high and low pressure sides and a motor for driving said compressor, and means for unloading and loading said compressor comprising a suction line connecting said low pressure side ofs'aid compressor with said evaporator, a check valve in said suction line, a chamber in said suction :line between said check valve and said compressor, said check valve being open during to cover all modifications normal operation of said compressor for permitting loading of said compressor from said evaporator, means effecting equalization of pressures between said high pressure side of said compressor and said low pressure side thereof when said compressor becomes idle, said equalization of pressures increasing the pressure on the cornpressor side of said check valve and thereby closing said check valve, said equalization of pressures filling said chamber and said suction line between said check valve and said low pressure side or" said compressor 'ith refrigerant charge substantially equal pressure to the refrigerant pressure at said high pressure side of said compressor whereby said compressor is unloaded, and the volume of said chamber and said suction line between said check valve and said low pressure side of said compressor being sufiicient to permit said motor to develop maximum torque when starting before the pressure of said charge between said check valve said suppressor is reduced by said compressor suthciently to eliect opening of said check valve and normal loading of said compressor.

3. In a refrigerating system including an evaporator, the combination of a refrigerating unit including a compressor having high and low pressure sides and a motor for driving said compressor, and means for unload' and loading said compressor comprising a suction line connecting said low pressure side of said compressor with said evaporator, a check valve in said suction line, a chamber in said suction line between said check valve and said compressor, said check valve being open during normal operation of said compressor for permitting loading of said compressor from said evaporator, means effecting equalization of pressures between said high pressure side of said compressor and said low pressure side thereof when said compressor becomes idle, said equalization of pressures increasing the pressure on the compressor side of said check valve and thereby closing said check valve, said equalization of pressures filling said chamber and said suction line between said check valve and said low pressure side of said compressor with a refrigerant charge substantially equal in pressure to the refrigerant pressure at said high pressure side of said compressor whereby said compressor is unloaded, and the volume of said chamber and said suction line between said check valve and said low pressure side of said corn pressor being at least equal to the capacity of said compressor during the period required by said compressor to come up to speed whereby said motor is permitted to develop maximum torque when starting before said charge in said chamber and suction line is reduced by said cornpressor sufficiently to effect opening of said check valve and normal loading of said compressor.

4. In a refrigerating system including an evaporator, the combination of a refrigerating unit including a com pressor having high and low pressure sides and a motor for driving said compressor, and means for unloading and loading said compressor comprising a suction line connecting said low pressure side of said compressor with said evaporator, a check valve in said suction line, a chamber in said suction line between said check valve and said compressor, said check valve being open during normal operation of said compressor for permitting loading of said compressor from said evaporator, means effecting equalization of pressures between said high pressure side of said compressor and said low pressure side thereof when said compressor becomes idle, said equalization of pressures increasing the pressure on the compressor side of said check valve and thereby closing said check valve, said equalization of pressures filling said chamber and said suction line between said check valve and said low pressure side of said compressor with a refrigerant charge substantially equal in pressure to the refrigerant pressure at said high pressure side of said compressor whereby said compressor is unloaded, and the volume of said chamber and said suction line between said check valve and said low pressure side of said compressor being greater than the capacity of said compressor during the period required by said motor to come up to speed whereby said motor is permitted to develop maximum torque when starting before said charge in said chamber and suction line is reduced by said compressor suficiently to efiect opening of said check valve and normal loading of said compressor.

5. In a refrigerating system including an evaporator, the combination of a refrigerating unit including a compressor having high and low pressure sides and a motor for driving said compressor, and n cans for unloading loading said compressor comprising a suction line connecting said low p essure side of said compressor with said evaporator, 21 check valve in said suction line, a chamber in said suction line between said check valve and said compressor, said check valve being open during normal operation of said compressor for permitting loading of said compressor from said evaporator, means effecting equalization of pressures between said high presmaximum torque when starting before said charge in said chamber and suction line is reduced by said compressor I opening of said check normal loading of said compressor.

References Cited in the file of this patent UNITED STATES PATENTS 

